Hi I am still kind of new at decorating, but all the cakes I have done have been in regualr buttercream. I was wondering how to go about changing the flavor up? I also have been wanting to do a whimsy cake, but i am very nervous. About how long does it take to bake it and put it together? One more question.....I have the most difficult time getting my buttercream really smooth. If you have any suggestions I would appreciate it!

If you are trying a new technique, it will vary on the time it will take you to do it. You should probably just put some time aside to practice. When I do a wedding cake, I bake the cake one day, crumb coat & frost the next & decorate the 3rd day.
As for getting buttercream smooth, there are many tips right here on this site to learn the techniques. Good luck!